The rich are different. The first time I turn up to interview Trudie Styler, her dog is ill and she's too upset to speak to me. I trail back through the freezing rush hour muttering bitterly about how most people have to carry on even when their dogs are dying - but then I'm not a dog person.

That was a Thursday evening. By the time I re-present myself first thing the following Monday, the Sumner family has returned from a glittering long weekend in St Petersburg. They partied at St Catherine's Palace with President Clinton and an assortment of what Styler describes as the 'seriously rich'. The man behind the event, entrepreneur Richard Caring, 'was a very generous host, who gave us an amazing weekend', (I spot four fur hats in the hall, which turn out to be party favours) and, in return, his guests raised £11 million in one evening for his charity for abused children.

Later that Monday evening, Styler and Sting are off to Los Angeles for another fundraiser. All this whizzing about in pursuit of parties and do-gooding is smoothed by a retinue of well-dressed staff. A terrifyingly elegant assistant opens the front door, a butler serves tea (two different butlers, in fact) and once Styler has broken the news that she cannot work on Thursday she leaves me to sort out another time with her diary secretary. Two PRs are in overkill-attendance.

Still, I get two opportunities to look at the house, which is amazing. It is an 18th-century terrace in London's St James's, but has, remarkably, the atmosphere of a Jacobean country house. There's velvet everywhere, and richly papered walls in reds and oranges and deep, dark chairs. The wood has been stripped back to its honey-coloured natural state, the lighting is dim, and a log fire burns in the grate of the front room that seems to double up as an office. (The elegant assistant keeps her laptop on an antique table there, anyway.) The fire, about whose environmental implications in central London I am uncertain, perfumes the house.

The house is also extremely warm, meaning that Styler doesn't need to be bundled up under several layers of woollies. She wears the two loveliest outfits I have ever seen on a fiftysomething: a black suit, stockings and patent shoes on Thursday and a pinstriped skirt, white shirt and long suede high-heeled boots on Monday. Sting was recently quoted as saying that he needed to make another album because 'my wife shops for Britain'. I mention this to her and she says:

'No, Europe.'

But we are here ostensibly to talk about olive oil and honey. The Sumners have started selling green, peppery organic oil, and delicate, soft honeys from their estate in Tuscany in an exclusive deal with Harrods. 'What's special about these products?' I ask, inviting her to promote them a bit. 'What's special about them?' she answers distractedly. 'I don't know how special they are. For me they're special, because I love eating from the land. I'm a control freak and I like to know what's gone into the soil.' And then she starts talking about her dad, who used to farm 110 acres, but as a farm manager for her uncle who wasn't an uncle and that's how her mum and dad met... 'I'm not being very articulate this morning,' she says finally. 'We've still got dog issues.'

It turns out that the dog, a handsome flat-coated retriever, is still alive, despite the belief on Thursday that he would have to be put down. 'I had a phone call just after you left. My London veterinary guy said there's a new chemotherapy for dogs that's come out in the last six months, which has been having quite good results with this particular sarcoma. So we're having a go, but he doesn't look very well at all today. And we're leaving for Los Angeles tonight, so I think we might have to...' She trails off, a bit tearfully. 'I'm very emotional about my animals. It's very sad. He's only six, and a great pal to Sting.'

Considering that Styler is effectively between planes and continents, and in a state of grief about the dog, she's looking stunning. Possibly it's the large glass of frothy green liquid she is drinking, which looks as though it's been drawn from a pond with an algae problem. She explains this away as 'broccoli and celery and things like that'. She also says she has 'a great yoga regime, and I meditate'. Pressed on the surgery front, she admits that 'I go to Dr Sebagh [the Wimpole Street aesthetic surgeon] and get these fantastic injection things that he gives, not under your skin, but he sort of prickles your skin, sort of like an amazing facial. And I do some Botox. If that's important.'

Well, I think it is, because Styler has that quality, not uncommon in rich women but almost never seen elsewhere, of actually looking better as she gets older. Though always perfectly presentable, she was, by her own admission, no very great beauty in her youth. But years of time and money and attention mean that she is now almost improbably slim and honed and beautifully turned out. If people like Styler and Sharon Osbourne keep improving in this way, one can only fear for the dysmorphia issues of the British menopausal female.

In Cooking from Lake House Organic Farm, the book Styler co-wrote with her chef, Joseph Sponzo in 1999, she describes herself and Sting sitting on the front step of an evening, 'just as we did as children. The doorstep might be a bit more grand, but basically we are the same.' To which one is inclined to reply: 'Get a grip, woman.' Basically, perhaps, Sting and Styler might be the same, but in all other respects they are not. They inhabit the planet rich and famous, and to pretend otherwise is disingenuous. The step belongs to a 16th-century manor house, with gardens which they have planted with 5,000 tulips, peonies, roses, clematis, and tissue poppies, a lake and water meadows, and painstakingly restored stucco ceilings and fireplaces.

When they tire of that, they can repair to the Tuscan villa - also 16th century - where, Styler reports happily, you can seat 30 people in the courtyard for dinner. When they bought it from someone she refers to as 'the duke' the house was falling into decline, but no longer. The marketing proposition for the olive oil and honey they are now producing from their original 900 acres hints faintly at the possibility of buying into their lifestyle: both Sting and Styler are mentioned on the packaging, which also refers to the Estate di Sumner. Their enthusiasm for the buying-in has its limits, however: when someone threatened to put a campsite on nearby land, they bought a further 600 acres to stop it.

As far as work is concerned, Styler says, 'I go where my heart takes me and my instinct takes me.' Heart and instinct seem to have no shortage of drive. Nowadays, Styler is best known professionally as a film producer, notably of Lock, Stock and Two Smoking Barrels. When we met, she'd just heard that her latest film, A Guide to Recognising Your Saints, written and directed by Dito Monteil, with Robert Downey Jr, had been shortlisted for the competition at the Sundance Film Festival. 'They had 1,300 entries and 14 go through. On 10 September, I'd been developing the film for four years, so I'm very happy.'

Her company was set up to produce first-time writer directors, but now she thinks she's had it with small films. 'In all the stuff I do, I really like it most when I'm being creative and collaborative, working with people who have my kind of energy around me. It was very isolating making this film for three of the four years. And the marketplace is deluged with stuff. More and more young people want to make films, which is a good thing, but means the market is very crowded. So I think when I produce from now on, I'll do it with other companies.'

She also made a foray into directing earlier this year, with a 15-minute film called Wait, which premiered in New York in December, part of a project sponsored by Glamour magazine to get four women who'd never directed before behind the camera. (The others were Gwyneth Paltrow, Jenny Bicks, who created Sex and the City, and Rosario Dawson.) 'I'd never thought of directing as an option for me. I don't know why, because I'm incredibly bossy. I was surprised how collaborative it is. As the producer, you have to get the money and schedule on time, and that's not what I do best. I have great people who help me be on time but I'm not an on-time person and I'm very chaotic in my thoughts.'

She also went back to acting, as Irene in the David Renwick [One Foot In The Grave]-scripted Love Soup. She was very good - surprisingly so to many, who couldn't really remember her as an actor. In fact, she'd wanted to act from the age of 14, and went to Bristol Old Vic drama school. 'I was always a show-off. I liked playing to the gallery, as my teachers used to say at school.' This is no doubt true (wallflowers don't ride to their weddings on horses) but it is also true that she's a control freak, and, like many performers, perhaps, performs partly in order to be seen on her own terms.

I wonder if her wealth gives her a sense of obligation, a kind of modern noblesse oblige. Once again, she takes the view that, deep down, she's still a kid on the front step - 'I grew up in a council house, as I expect you know. I come from a modest background where paying rent was problematic. Though there wasn't much money, my mum was generous. She was very religious and she cleaned the church steps, put flowers on the altar, filled her envelopes at Christmas. She always said she didn't mind how we did in exams, as long as we did our best, but what she did care about was giving back for the life we'd been given. When I entered this lifestyle, being with Sting, living a very comfortable life, I did think it was time to make a contribution.'

Styler is flying to Los Angeles this evening to attend the Snowflake Ball in aid of Unicef and be presented with an award. 'It's called the Danny Kaye Humanitarian Award. I'll give a speech about the things I've seen, experiences I've had, in Ecuador and Sri Lanka, and the photographs I took will be there, and we'll raise a lot of money.' After visiting children living on the rubbish dumps in Ecuador, she pledged that she'd raise £1 million in three years. 'I was so moved, I had this huge energy to go away and raise a million quid very quickly, which I did by asking Sting if he would do a concert, which he did in London, and we raised £900,000 that night.'

She also fits in being wife to Sting, which presumably involves quite a lot of tantric sex (obviously, she isn't going to tell me), as well as a fair bit of dashing around. 'I don't tour with him any more but we don't like to be more than a couple of weeks apart so I do try to catch up with him. We have homes in America [on both East and West Coasts] so it does involve a fair bit of going backwards and forwards.' She is also mother to their four children. Jake, 20, the second, wanders downstairs at the end of our interview and kisses his mum. He is home for the weekend from New York where, like his older sister Mickey, he is at college. The 15-year-old, Coco, is at boarding school, and the youngest, Giacomo, 10, at day school in London.

I ask Styler if all her friends are famous (she mentions Bob Geldof and 'Guy' at various points in the conversation) and she insists not. She sometimes sees her sisters, one of whom is a mum in Edinburgh and the other a nurse, but she is not close to them. I leave for the second time thinking that Trudie Styler would probably be interesting and quite good fun if you could get to know her. But she's on that other planet, and it's subject to different laws of physics.

The Il Palagio range of extra virgin olive oil and honey is available exclusively at Harrods, 020 7730 1234; Harrods.com